Coin-shaped cell, and manufactuing method thereof

ABSTRACT

A positive electrode plate ( 11 ) and a negative electrode plate ( 12 ) are coiled around into a flat shape such that positive electrode layer faces ( 22   a - 22   e ) and negative electrode layer faces ( 23   a - 23   f ) are alternately layered upon one another with a separator interposed therebetween. Positional discrepancy detecting holes ( 41   a   , 41   b   , 42, 43, 44 ) are formed in the positive electrode layer faces ( 22   a   , 22   b ) and negative electrode layer face ( 23   a ) facing each other at the coiling start end, and in the positive electrode layer face ( 22   e ) and negative electrode layer face ( 23   f ) facing each other at the coiling finish end. The electrode plates are coiled into an electrode plate group, which is subjected to X-ray inspection for detecting positional displacement based on a discrepancy in the positions of the holes.

TECHNICAL FIELD

[0001] The present invention relates to a coin type battery and amanufacturing method thereof. The invention relates particularly to acoin type battery having an electrode plate group of a coiled structureconstructed with a positive electrode plate, a negative electrode plate,and a separator interposed therebetween.

BACKGROUND ART

[0002]FIG. 9 illustrates the most commonly adopted electrode platestructure for coin type batteries, in which a disk-shaped positiveelectrode pellet 32 and a negative electrode pellet 33 are arrangedface-to-face with a separator 34 interposed in between them. This cointype battery is manufactured through the following process steps to havethe coin-like appearance: The positive electrode pellet 32, separator34, and negative electrode pellet 33 are placed in the face-to-facearrangement inside a sealing case 35 of circular half shell form, liquidelectrolyte is injected, a gasket 36 is fitted to a lateral periphery ofthe sealing case 35, a cap case 31 is coupled onto the sealing case, andthe open end edge of the cap case 31 is crimped or bent inwards so as totightly seal the battery inner space.

[0003] Batteries having such electrode plate structure as describedabove wherein one positive electrode pellet 32 and one negativeelectrode pellet 33 are arranged face-to-face with each other cannothave a large discharge capacity because of the small reaction area wherethe positive and negative electrode plates face each other. To achieve alarger discharge capacity, positive and negative electrode plates mustface each other in a larger area, and accordingly, for relatively largerbatteries other than coin type batteries, various structures thatenlarge the reaction area have widely been adopted in an attempt toincrease the battery energy density in high rate discharge performance.There is, for example, a layered structure in which a plurality ofpositive and negative electrode plates are layered upon one another withseparators interposed therebetween. Another example is a coiledstructure in which strips of positive and negative electrode plates arecoiled together with a separator interposed therebetween. The dischargecapacity of coin type battery could be increased if electrode plates ofsuch a layered or coiled structure were accommodated in a coin-shaped,flat case. In fact, the applicants of the present invention haveproposed a battery containing an electrode plate group of a coiledstructure in a coin-shaped, flat case in Japanese Patent Laid-OpenApplications Nos. 2000-241678 and 2000-241679.

[0004] This electrode plate group of the coiled structure is constructedas shown in FIG. 10A and FIG. 10B: A positive electrode plate 7 consistsof a plurality of positive electrode layer faces 17 a-17 e coupledtogether by connecting pieces 19 a-19 d, and a negative electrode plate8 consists of a plurality of negative electrode layer faces 18 a-18 ethat are larger than the positive electrode layer faces 17 a-17 e andcoupled together by connecting pieces 20 a-20 d. They are coiled aroundwith a separator interposed between them into a flat shape so as to beaccommodated in a circular case. The resultant flat shape electrodeplate group 1 appears as shown in FIG. 11. As shown in FIG. 12, thiselectrode plate group 1 is encased in a sealing case 5, a negativeelectrode lead 16 is welded to an inner face of the sealing case 5, anda positive electrode lead 15 is welded to a cap case 4. The sealing case5 is then filled with liquid electrolyte. A gasket 6 is fitted to alateral periphery of the sealing case 5, the cap case 4 is coupledthereon, and the open end edge of the cap case 4 is crimped so as totightly seal the battery inner space. Such coin type battery can beconstructed both as a lithium primary battery and rechargeable battery.Such a small and flat shape battery capable of outputting a largedischarge current can contribute to realization of even smaller portableelectronic devices and the like with higher functionalities.

[0005] One problem is that, in the manufacture of the electrode plategroup 1, the positive and negative electrode plates 7, 8 are not fixedin position relative to each other, and they can easily be displaced inthe process step of coiling them into a flat shape. If the positiveelectrode layer faces 17 a-17 e upon the negative electrode layer faces18 a-18 e are largely offset because of the displacement during thecoiling process, there is a risk of internal short-circuiting caused bydendritic growth of lithium. Since the coin type battery contains acoiled electrode plate group 1 in a small, flat case, internalshort-circuiting may also be caused if the electrode plates are not inregister, as they may contact the sealing case 5 upon an impact of afalling accident or the like.

[0006] Accordingly, it is necessary to detect the presence ofdiscrepancy in position between the positive electrode layer faces 17a-17 e and negative electrode layer faces 18 a-18 e, which is, however,not possible after the positive and negative electrode plates 7, 8 havebeen coiled around with the separator therebetween, because the finishedelectrode plate group 1 is covered by the separator that is unified withthe electrode plates. Thus there is a need to inspect, by some means,whether there is a discrepancy in position between the positiveelectrode layer faces 17 a-17 e and negative electrode layer faces 18a-18 e, so that only the electrode plate groups 1 that are within apermissible range of positional displacement are used for assembling thebatteries.

[0007] An object of the present invention is to provide a coin typebattery having a feature that enables detection of positionaldisplacement between positive and negative electrode plates of anassembled electrode plate group, and a manufacturing method of this cointype battery.

DISCLOSURE OF THE INVENTION

[0008] To achieve the above object, according to a first aspect of thepresent invention, there is provided a coin type battery comprising:

[0009] a strip of positive electrode plate formed of a plurality ofpositive electrode layer faces coupled together by a plurality ofconnecting pieces;

[0010] a strip of negative electrode plate formed of a plurality ofnegative electrode layer faces coupled together by a plurality ofconnecting pieces;

[0011] a separator interposed between the positive electrode plate andthe negative electrode plate, the positive electrode plate and negativeelectrode plate being folded at the respective connecting pieces andcoiled around into an electrode plate group of flat form such that thepositive electrode layer faces and the negative electrode layer facesare alternately layered upon one another with the separator interposedtherebetween;

[0012] a sealing case forming an inner space together with a gasket anda cap case for accommodating the electrode plate group, characterized inthat

[0013] the positive electrode plate and the negative electrode plate arerespectively formed with positional discrepancy detecting cut-outs fordetecting positional displacement between the positive electrode layerfaces and the negative electrode layer faces when both electrode platesare coiled around. Preferably, the positional discrepancy detectingcut-outs are holes, centers of which conform to each other when thepositive electrode plate and negative electrode plate are coiled aroundin exact register. Alternatively, the positional discrepancy detectingcut-outs can be notches of same or similar form, peripheral edges ofwhich conform to each other when the positive electrode plate andnegative electrode plate are coiled around in exact register.

[0014] According to the above structure, after coiling around thepositive and negative electrode plates formed with positionaldiscrepancy detecting cut-outs into the electrode plate group of flatform, X-ray inspection is carried out to detect positional displacementin the positive and negative electrode plates based on the positionalrelationship between the positional discrepancy detecting cut-outs inthe electrode plates. Non-conforming electrode plate groups in whichpositional displacement has occurred may cause short circuits if encasedand assembled into coin type batteries. The inspection enables only theelectrode plate groups that fall in a permissible range of positionaldisplacement to be assembled into coin type batteries. Thus, coin typebatteries constructed with coiled electrode plates are manufactured witha good yield.

[0015] According to a second aspect of the invention, there is alsoprovided a coin type battery comprising:

[0016] a strip of positive electrode plate formed of a plurality ofpositive electrode layer faces coupled together by a plurality ofconnecting pieces;

[0017] a strip of negative electrode plate formed of a plurality ofnegative electrode layer faces coupled together by a plurality ofconnecting pieces;

[0018] a separator interposed between the positive electrode plate andthe negative electrode plate, the positive electrode plate and negativeelectrode plate being folded at the respective connecting pieces andcoiled around into an electrode plate group of flat form such that thepositive electrode layer faces and the negative electrode layer facesare alternately layered upon one another with the separator interposedtherebetween;

[0019] a sealing case forming an inner space together with a gasket anda cap case for accommodating the electrode plate group, characterized inthat

[0020] the electrode plate group is provided, at least in one positiveelectrode layer face and one negative electrode layer face that faceeach other at a coiling finish end, or at least in the positiveelectrode layer faces and the negative electrode layer faces that faceeach other at a coiling start end and at a coiling finish end, withpositional discrepancy detecting cut-outs for detecting positionaldisplacement between the positive electrode layer face and the negativeelectrode layer face when both electrode plates are coiled around. Thepositional discrepancy detecting cut-outs can be either holes or notchesas mentioned above.

[0021] According to the above structure, after coiling around thepositive and negative electrode plates formed with positionaldiscrepancy detecting cut-outs in their respective layer faces into theelectrode plate group, X-ray inspection is carried out to detectpositional displacement in the positive and negative electrode platesbased on the positional relationship between the positional discrepancydetecting cut-outs in the opposing positive and negative electrode layerfaces. Thus, short circuits that may occur after encasing and assemblingthe electrode plate group into the coin type battery is prevented, andcoin type batteries constructed with coiled electrode plates aremanufactured with a good yield.

[0022] In the battery above, the positive electrode plate and thenegative electrode plate are coiled around such that a first positiveelectrode layer face is placed upon a negative electrode layer face thatis second from the coiling start end; a first negative electrode layerface is folded back at a first connecting piece upon the first positiveelectrode layer face; the first negative electrode layer face is furtherfolded back at a second connecting piece upon a second positiveelectrode layer face. The positional discrepancy detecting cut-outs areformed in the first negative electrode layer face and the first andsecond positive electrode layer faces that face the first negativeelectrode layer face. The layer faces of positive and negative electrodeplates are thus layered alternately, and a positional discrepancy at thecoiling start end is reliably detected.

[0023] The negative electrode layer faces are formed larger than thepositive electrode layer faces, and the positional discrepancy detectingcut-outs are formed as holes or notches. The holes or notches formed ineither one of the positive electrode layer faces and the negativeelectrode layer faces are larger than the holes or notches formed in theother, and their positional relationship is determined based on apermissible range of positional displacement between the positiveelectrode plate and the negative electrode plate. The positionalrelationship, i.e., whether the smaller detecting hole is located insidethe larger detecting hole, can be detected from transmitted X-ray imagesobtained by irradiating X-rays to the electrode plate group in thelayering direction. X-ray inspection thus enables determination ofwhether the positional displacement is within the permissible range ornot.

[0024] The positional discrepancy detecting cut-outs respectively formedin the first and the second positive electrode layer faces are formed indifferent sizes. Thereby, a positional discrepancy between the first andsecond layer faces of the positive electrode at its coiling start end isdetected.

[0025] The detecting holes formed in the positive electrode layer facesare larger than the holes in the negative electrode layer faces. Thatway, it is prevented that the negative electrode layer face is offsetfrom the positive electrode layer face. When constructing the battery asa lithium rechargeable battery, this will prevent dendritic growth oflithium.

[0026] The positional discrepancy detecting cut-outs formed in thepositive electrode layer face and the negative electrode layer face thatface each other at the coiling start end and the positional discrepancydetecting cut-outs formed in the positive electrode layer face and thenegative electrode layer face that face each other at the coiling finishend are located at different positions on the positive electrode layerfaces and the negative electrode layer faces. Thereby, positionaldisplacement at the coiling start end and the coiling finish end isdetected at the same time in the X-ray inspection.

[0027] According to a third aspect of the invention, there is furtherprovided a method of manufacturing a coin type battery, comprising:

[0028] folding a strip of positive electrode plate formed of a pluralityof positive electrode layer faces coupled together by a plurality ofconnecting pieces, and a strip of negative electrode plate formed of aplurality of negative electrode layer faces coupled together by aplurality of connecting pieces at the respective connecting pieces andcoiling it around into an electrode plate group of flat form such thatthe positive electrode layer faces and the negative electrode layerfaces are alternately layered upon one another with a separatorinterposed therebetween;

[0029] accommodating the electrode plate group into a sealing case;

[0030] injecting liquid electrolyte thereinto;

[0031] placing a cap case onto the sealing case via a gasket; and

[0032] crimping the cap case to seal the inside of the sealing case,characterized in that

[0033] the positive electrode plate and the negative electrode plate arerespectively formed with positional discrepancy detecting cut-outs fordetecting positional displacement between the positive electrode layerfaces and the negative electrode layer faces when both electrode platesare coiled around;

[0034] after coiling around the positive electrode plate and thenegative electrode plate into the electrode plate group, X-rays areirradiated thereto in a direction in which the electrode plates arelayered so as to obtain transmitted X-ray images of the electrode plategroup;

[0035] a positional discrepancy is detected, by processing the images,between the positional discrepancy detecting cut-outs in the positiveelectrode layer faces and the positional discrepancy detecting cut-outsin the negative electrode layer faces; and

[0036] when the detected positional discrepancy is within apredetermined permissible range, the electrode plate group isaccommodated in the sealing case.

[0037] According to the above method of manufacturing coin typebatteries, electrode plate groups formed with positional discrepancydetecting cut-outs are subjected to X-ray inspection for selecting thegroups in which no positional displacement has occurred between thepositive and negative electrode plates, and these groups are encased andassembled into coin type batteries. Short circuits that may be caused bypositional displacement after completing the batteries is thusprevented, and coin type batteries constructed with electrode plates ofa coiled structure are manufactured with a good yield.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038]FIG. 1 is a cross section illustrating the structure of a cointype battery according to one embodiment of the present invention;

[0039]FIG. 2A is a top plan view of a negative electrode plate, and FIG.2B is a top plan view of a positive electrode plate;

[0040]FIG. 3A to FIG. 3C are model views illustrating a coiling processstep in order;

[0041]FIG. 4 is a model view of an electrode plate group in the coiledstate;

[0042]FIG. 5 is a model view illustrating the face-to-face arrangementof positional discrepancy detecting holes;

[0043]FIG. 6 is an image view of an electrode plate group subjected toX-ray inspection;

[0044]FIG. 7A is a top plan view of a negative electrode plate accordingto another embodiment of the invention, and FIG. 7B is a top plan viewof a positive electrode plate of the same;

[0045]FIG. 8 is an image view of the electrode plate group of the sameembodiment subjected to X-ray inspection;

[0046]FIG. 9 is a cross section illustrating the structure of aconventional coin type battery;

[0047]FIG. 10A is a top plan view of a conventional negative electrodeplate, and FIG. 10B is a top plan view of a conventional positiveelectrode plate;

[0048]FIG. 11 is a top plan view of a conventional electrode plate groupof a coiled structure; and

[0049]FIG. 12 is a cross section of a conventional coin type batterythat uses the electrode plate group of the coiled structure.

BEST MODE FOR CARRYING OUT THE INVENTION

[0050] Preferred embodiments of the present invention will be describedbelow with reference to the accompanying drawings for a betterunderstanding of the present invention. It should be noted that theembodiments described below are merely examples of carrying out theinvention and should not pose any limitation on the technical scope ofthe invention.

[0051] The coin type battery according to this embodiment ismanufactured through the following process steps: An electrode plategroup 10 is encased in a sealing case 5 of circular half shell form asshown in FIG. 1, a positive electrode lead 26 and a negative electrodelead 27 drawn out from the electrode plate group 10 are welded to a capcase 4 and the sealing case 5, respectively, liquid electrolyte isinjected, a gasket 6 is fitted to a lateral periphery of the sealingcase 5, the cap case 4 is coupled upon the gasket 6, and the open endedge of the cap case 4 is crimped or bent inwards so as to tightly sealthe battery inner space.

[0052] The electrode plate group 10 is constructed in a flat coiledshape with wound positive and negative electrode plates 11, 12 and aseparator interposed therebetween: The negative electrode plate 12consists of six negative electrode layer faces 23 a-23 f coupledtogether by connecting pieces 25 a-25 e and the negative electrode lead27 formed at the coiling finish end, as shown in FIG. 2A. The positiveelectrode plate 11 consists of five positive electrode layer faces 22a-22 e that are smaller than the negative electrode layer faces 23 a-23f and coupled together by connecting pieces 24 a-24 d and the positiveelectrode lead 26 formed at the coiling finish end, as shown in FIG. 2B.Coiling is achieved by folding the electrode plates at their connectingpieces 24 a-24 d and 25 a-25 e such that the positive electrode layerfaces 22 a-22 e and negative electrode layer faces 23 a-23 f arealternately layered upon one another with the separator in between them.The following is a description of how the positive electrode layer faces22 a-22 e and negative electrode layer faces 23 a-23 f are alternatelylayered upon one another with the separator in between them in thecoiling process steps:

[0053] As shown in FIG. 3A, the separator 13 illustrated by broken linesis provided to cover both faces of the positive electrode plate 11,which is placed upon the negative electrode plate 12, such that thefirst positive electrode layer face 22 a is located upon a negativeelectrode layer face 23 b that is second from the coiling start end. Thenegative electrode layer face 23 a is then folded back at the connectingpiece 25 a on the positive electrode layer face 22 a as shown in FIG.3B. This portion where the positive electrode layer face 22 a issandwiched between the negative electrode layer faces 23 a, 23 b via theseparator 13 on both sides is folded back at the connecting pieces 24 aand 25 b on the next positive electrode layer face 22 b that issuperposed on the negative electrode layer face 23 c as shown in FIG.3C. This folding process is repeated towards the coiling finish end,until the positive and negative electrode plates 11, 12 are coiledaround in a flat shape into an electrode plate group 10 shown in FIG. 4,with the separator 13 therebetween.

[0054] When coiling around the positive and negative electrodes 11, 12into a flat electrode plate group 10 as described above, if theelectrode plates 11, 12 are not in register, there may be a discrepancyin face-to-face positions of the positive electrode layer faces 22 a-22e and negative electrode layer faces 23 a-23 f. If part of the positiveelectrode layer faces 22 a-22 e upon the negative electrode layer faces23 a-23 f is offset because of the positional discrepancy, there arerisks of internal short-circuiting caused by dendritic growth oflithium, or of internal short-circuiting across the electrode plates andsealing case 5 upon an impact of a falling accident or the like.Consequently, it is necessary to detect whether there is a positionaldiscrepancy in the finished electrode plate group 10. For this purpose,the positive and negative electrode plates 11, 12 are respectivelyprovided with positional discrepancy detecting holes or cut-outs 41 a,41 b, 42 and 43, 44 in the positive electrode layer faces 22 a, 22 b andnegative electrode layer face 23 a that face each other at the coilingstart end, and in the positive electrode layer face 22 e and negativeelectrode layer face 23 f that face each other at the coiling finishend.

[0055] Since the negative electrode layer face 23 a faces the positiveelectrode layer faces 22 a, 22 b at the coiling start end as describedabove, when the electrode plates are coiled together in exact register,the positional discrepancy detecting hole 43 in the negative electrodelayer face 23 a is concentric with the holes 41 a, 41 b respectivelyformed in the positive electrode layer faces 22 a, 22 b as shown in FIG.4 and FIG. 5. At the coiling finish end where the positive electrodelayer face 22 e faces the negative electrode layer face 23 f, thepositional discrepancy detecting hole 44 in the negative electrode layerface 23 f is concentric with the hole 42 formed in the positiveelectrode layer face 22 e as shown in FIG. 5, when the electrode platesare coiled together in exact register. FIG. 5 is a model viewillustrating a cross section that is orthogonal to the cross section ofFIG. 4. The purpose of presenting a cross section in this direction isto illustrate the positions of the detecting holes at the coiling startend and coiling finish end that are offset in a direction orthogonal tothe coiling direction.

[0056] Since the diameter of the layer faces 23 a-23 f of the negativeelectrode plate 12 in the direction of its width is larger than that ofthe layer faces 22 a-22 e of the positive electrode plate 11, apositional discrepancy of the positive electrode plate 11 in the widthdirection of the negative electrode plate 12 should be allowable inphysical terms by the difference in the widthwise diameter. Thewidthwise diameter of the negative electrode layer faces 23 a-23 f inthis embodiment is 24.0 mm, while that of the positive electrode layerfaces 22 a-22 e is 22.0 mm, and therefore a positional discrepancy ofpositive electrode layer faces 22 a-22 e on the negative electrode layerfaces 23 a-23 f should be allowable by 1.0 mm on both sides in thewidthwise direction. However, it is preferable to ensure that positiveelectrode layer faces 22 a-22 e are placed exactly upon the negativeelectrode layer faces 23 a-23 f in order to suppress the dendriticgrowth of lithium. If the edges of the positive electrode layer faces 22a-22 e conform to the edges of the negative electrode layer faces 23a-23 f, it is likely that a short circuit is formed upon an impact of afalling accident or the like. For this reason, in this embodiment, thepermissible range of positional discrepancy is determined by thediameters of the detecting holes 41 a, 41 b, 42 in the positiveelectrode and those 43, 44 in the negative electrode.

[0057] The diameter of the detecting holes 41 a, 41 b, 42 in thepositive electrode is set larger than the detecting holes 43, 44 in thenegative electrode, and if the detecting holes 43, 44 are located insidethe detecting holes 41 a, 41 b, 42 with a certain clearance, it isjudged that the positional discrepancy is within the permissible range.In this embodiment, the diameter of the detecting holes 41 a, 42 in thepositive electrode is 3.2 mm, and that of the hole 41 b is 4.2 mm. Thediameter of the detecting hole 43 in the negative electrode is 1.5 mm.When the detecting hole 41 a in the positive electrode is not inside itsdetecting hole 41 b, it is assumed that there has been a positionaldiscrepancy when folding the positive electrode plate 11 at itsconnecting piece 24 a shown in FIG. 3C. If the positional discrepancybetween the centers of the detecting hole 41 a in the positive electrodeand the hole 43 in the negative electrode at the coiling start end iswithin 0.65 mm and if the discrepancy between the centers of the hole 42in the positive electrode and the hole 44 in the negative electrode iswithin 0.65 mm, they are within the permissible range.

[0058] Detection of positional discrepancy using these detecting holes41 a, 41 b, 42 and 43, 44 in the positive and negative electrodes isachieved by irradiating X-rays to the complete electrode plate group 10and by processing the transmitted X-ray images of the electrode plategroup 10. FIG. 6 is an example of an image obtained by X-raytransmission; it shows a state in which both electrode plates are inexact register where the centers of the detecting holes 41 a, 41 b, 42in the positive electrode and those of the detecting holes 43, 44 in thenegative electrode coincide with each other. Since the detecting holes41 a, 41 b in the positive electrode and the hole 43 in the negativeelectrode at the coiling start end and the detecting holes 42, 44 at thecoiling finish end are formed at different positions, it is possible toseparately detect a positional discrepancy at the coiling start/finishends.

[0059] Determination of non-conforming electrode plate groups 10 usingthe transmitted X-ray images can be made based on whether a positionaldiscrepancy is detected between the centers of the detecting hole 41 ain the positive electrode and of the hole 43 in the negative electrode,and between the centers of the detecting hole 42 in the positiveelectrode and of the hole 44 in the negative electrode. Alternatively,it can be made based on whether the detecting hole 41 a in the positiveelectrode is located inside its detecting hole 41 b and by detecting theminimum distance between the peripheral edges of the detecting hole 41 ain the positive electrode and the hole 43 in the negative electrode, andbetween the peripheral edges of the detecting hole 42 in the positiveelectrode and the hole 44 in the negative electrode.

[0060] The diameter of the detecting holes 41 a, 42 in the positiveelectrode is 3.2 mm in this embodiment as mentioned above, while thediameter of the detecting holes 43, 44 in the negative electrode is 1.5mm. In the case where the inspection is based on detected minimumdistances between the peripheral edges of the detecting hole 41 a in thepositive electrode and the hole 43 in the negative electrode, andbetween the peripheral edges of the detecting hole 42 in the positiveelectrode and the hole 44 in the negative electrode, if it is detectedfrom a processed image of transmitted X-rays that these minimumdistances are 0.2 mm or more, it is determined that the positionaldiscrepancy is within the permissible range, and the electrode plategroup 10 is identified as a conforming product that can be assembledinto a coin type battery. If the detected minimum distances are 0.2 mmor less, then the electrode plate group 10 is disposed as anon-conforming product in which large positional displacement hasoccurred.

[0061] In the embodiment described above, the holes for detectingpositional displacement formed at the coiling start/finish ends areoffset from each other in a direction orthogonal to the coilingdirection, but they may be offset from each other along the coilingdirection.

[0062] In the embodiment described above, the holes 41 a, 41 b, 42, 43,44 or cut-outs for detecting positional displacement are of circularform, but they can be in other forms such as squares. Alternatively,they can be formed as notches 71 a, 71 b, 72, 73, 74 as shown in FIG. 7Aand FIG. 7B. The positional discrepancy detecting cut-outs may be formedonly in the positive and negative electrode layer faces that face eachother at the coiling finish end of the electrode plate group. In thecase where the positional discrepancy detecting cut-outs are formed bothat the coiling start/finish ends of the electrode plate group, they maybe provided only to the first positive electrode layer face 22 a, unlikethe case shown in FIG. 2A and FIG. 2B in which the first layer face 22 aand the second layer face 22 b of the positive electrode are both formedwith the cut-outs. Forming notches has an advantage over the forming ofholes in that electrode plate punching die set can be simplified.

[0063] The positive and negative electrode plates 11, 12 shown in FIG.7A and FIG. 7B have basically the same configuration as thoseillustrated in FIG. 2A and FIG. 2B; the negative electrode layer facesare larger than the positive electrode layer faces. At the coiling startend, positional discrepancy detecting cut-outs or notches 71 a, 71 b and73 are formed in a right-angled triangular shape in the layer faces 22a, 22 b of the positive electrode plate 11 and in the layer face 23 a ofthe negative electrode plate 12, respectively, at matching positions. Inthe positive electrode layer face 22 e and negative electrode layer face23 f that face each other at the coiling finish end, positionaldiscrepancy detecting cut-outs or notches 72, 74 are formed in aright-angled triangular shape. The notches 71 a, 71 b, 73 and 72, 74shown in FIG. 7A and FIG. 7B are all of the same shape, so that, whenthe positive and negative electrode plates 11, 12 are coiled around inexact register, the straight portions of matching notches aresubstantially in parallel to each other. Alternatively, matching notchescan be formed in shapes analogous to each other.

[0064]FIG. 8 illustrates an image obtained by transmitted X-rays of anelectrode plate group having these positive and negative electrodeplates 11, 12. It can be seen from the drawing that a positionaldiscrepancy in the electrode plate group at its coiling start/finishends are detected based on the relative positional relationships betweenthe corresponding detecting notches 71 a, 71 b, 73 and 72, 74. Thenotches can be in some other forms such as arcs or the like other thanright-angled triangles.

Industrial Applicability

[0065] As described above, according to the present invention, it ispossible to detect positional displacement in a coiled electrode plategroup that is applied to flat shaped batteries such as coin typebatteries. It prevents short circuits caused by positional displacementof electrode plates, and is advantageously adopted for the manufactureof coin type batteries with a good yield.

1. A coin type battery comprising: a strip of positive electrode plate(11) formed of a plurality of positive electrode layer faces (22 a-22 e)coupled together by a plurality of connecting pieces (24 a-24 d); astrip of negative electrode plate (12) formed of a plurality of negativeelectrode layer faces (23 a-23 f) coupled together by a plurality ofconnecting pieces (25 a-25 e); a separator (13) interposed between thepositive electrode plate and the negative electrode plate, the positiveelectrode plate and negative electrode plate being folded at therespective connecting pieces (24 a-24 d, 25 a-25 e) and coiled aroundinto an electrode plate group (10) of flat form such that the positiveelectrode layer faces (22 a-22 e) and the negative electrode layer faces(23 a-23 f) are alternately layered upon one another with the separatorinterposed therebetween; a sealing case (5) forming an inner spacetogether with a gasket (6) and a cap case (4) for accommodating theelectrode plate group, characterized in that the positive electrodeplate (11) and the negative electrode plate (12) are respectively formedwith positional discrepancy detecting cut-outs (41 a, 41 b, 42, 43, 44,71 a, 71 b, 72, 73, 74) for detecting positional displacement betweenthe positive electrode layer faces (22 a-22 e) and the negativeelectrode layer faces (23 a-23 f) when both electrode plates (11, 12)are coiled around.
 2. The coin type battery according to claim 1,wherein the positional discrepancy detecting cut-outs are holes (41 a,41 b, 42, 43, 44), centers of which conform to each other when thepositive electrode plate (11) and negative electrode plate (12) arecoiled around in exact register.
 3. The coin type battery according toclaim 1, wherein the positional discrepancy detecting cut-outs arenotches (71 a, 71 b, 72, 73, 74) of same or similar form, peripheraledges of which conform to each other when the positive electrode plate(11) and negative electrode plate (12) are coiled around in exactregister.
 4. A coin type battery comprising: a strip of positiveelectrode plate (11) formed of a plurality of positive electrode layerfaces (22 a-22 e) coupled together by a plurality of connecting pieces(24 a-24 d); a strip of negative electrode plate (12) formed of aplurality of negative electrode layer faces (23 a-23 f) coupled togetherby a plurality of connecting pieces (25 a-25 e); a separator (13)interposed between the positive electrode plate and the negativeelectrode plate, the positive electrode plate and negative electrodeplate being folded at the respective connecting pieces (24 a-24 d, 25a-25 e) and coiled around into an electrode plate group (10) of flatform such that the positive electrode layer faces (22 a-22 e) and thenegative electrode layer faces (23 a-23 f) are alternately layered uponone another with the separator interposed therebetween; a sealing case(5) forming an inner space together with a gasket (6) and a cap case (4)for accommodating the electrode plate group, characterized in that theelectrode plate group (10) is provided, at least in one positiveelectrode layer face (22 e) and one negative electrode layer face (23 f)that face each other at a coiling finish end, with positionaldiscrepancy detecting cut-outs (42, 72, 44, 74) for detecting positionaldisplacement between the positive electrode layer face (22 e) and thenegative electrode layer face (23 f) when both electrode plates (11, 12)are coiled around.
 5. A coin type battery comprising: a strip ofpositive electrode plate (11) formed of a plurality of positiveelectrode layer faces (22 a-22 e) coupled together by a plurality ofconnecting pieces (24 a-24 d); a strip of negative electrode plate (12)formed of a plurality of negative electrode layer faces (23 a-23 f)coupled together by a plurality of connecting pieces (25 a-25 e); aseparator (13) interposed between the positive electrode plate and thenegative electrode plate, the positive electrode plate and negativeelectrode plate being folded at the respective connecting pieces (24a-24 d, 25 a-25 e) and coiled around into an electrode plate group (10)of flat form such that the positive electrode layer faces (22 a-22 e)and the negative electrode layer faces (23 a-23 f) are alternatelylayered upon one another with the separator interposed therebetween; asealing case (5) forming an inner space together with a gasket (6) and acap case (4) for accommodating the electrode plate group, characterizedin that the electrode plate group (10) is provided, at least in thepositive electrode layer faces (22 a, 22 b, 22 e) and the negativeelectrode layer faces (23 a, 23 f) that face each other at a coilingstart end and at a coiling finish end, with positional discrepancydetecting cut-outs (41 a, 41 b, 42, 43, 44, 71 a, 71 b, 72, 73, 74) fordetecting positional displacement between the positive electrode layerfaces (22 a, 22 b, 22 e) and the negative electrode layer faces (23 a,23 f) when both electrode plates (11, 12) are coiled around.
 6. The cointype battery according to claim 5, wherein the positional discrepancydetecting cut-outs are holes (41 a, 41 b, 42, 43, 44), centers of whichconform to each other when the positive electrode plate (11) andnegative electrode plate (12) are coiled around in exact register. 7.The coin type battery according to claim 5, wherein the positionaldiscrepancy detecting cut-outs are notches (71 a, 71 b, 72, 73, 74) ofsame or similar form, peripheral edges of which conform to each otherwhen the positive electrode plate (11) and negative electrode plate (12)are coiled around in exact register.
 8. The coin type battery accordingto claim 5, wherein the positive electrode plate (11) and the negativeelectrode plate (12) are coiled around such that a first positiveelectrode layer face (22 a) is placed upon a negative electrode layerface (23 b) that is second from the coiling start end; a first negativeelectrode layer face (23 a) is folded back at a first connecting piece(25 a) upon the first positive electrode layer face (22 a); the firstnegative electrode layer face (23 a) is further folded back at a secondconnecting piece (25 b) upon a second positive electrode layer face (22b), and wherein the positional discrepancy detecting cut-outs (43, 41 a,41 b) are formed in the first negative electrode layer face (23 a) andthe first and second positive electrode layer faces (22 a, 22 b) thatface the first negative electrode layer face.
 9. The coin type batteryaccording to claim 1, wherein the negative electrode layer faces (23a-23 f) are formed larger than the positive electrode layer faces (22a-22 e), and wherein the positional discrepancy detecting cut-outs areformed as holes or notches, the holes or notches formed in either one ofthe positive electrode layer faces (22 a, 22 b, 22 e) and the negativeelectrode layer faces (23 a, 23 f) being larger than the holes ornotches formed in the other, their positional relationship beingdetermined based on a permissible range of positional displacementbetween the positive electrode plate (11) and the negative electrodeplate (12).
 10. The coin type battery according to claim 8, wherein thepositional discrepancy detecting cut-outs (41 a, 41 b) respectivelyformed in the first and the second positive electrode layer faces (22 a,22 b) are formed in different sizes.
 11. The coin type battery accordingto claim 6, wherein the holes (41 a, 41 b, 42) formed in the positiveelectrode layer faces (22 a, 22 b, 22 e) are larger than the holes (43,44) in the negative electrode layer faces (23 a, 23 f).
 12. The cointype battery according to claim 5, wherein the positional discrepancydetecting cut-outs (41 a, 41 b, 43, 71 a, 71 b, 73) formed in thepositive electrode layer faces (22 a, 22 b) and the negative electrodelayer face (23 a) that face each other at the coiling start end and thepositional discrepancy detecting cut-outs (42, 44, 72, 74) formed in thepositive electrode layer face (22 e) and the negative electrode layerface (23 f) that face each other at the coiling finish end are locatedat different positions on the positive electrode layer faces (22 a, 22b, 22 e) and the negative electrode layer faces (23 a, 23 f).
 13. Amethod of manufacturing a coin type battery, comprising: folding a stripof positive electrode plate (11) formed of a plurality of positiveelectrode layer faces (22 a-22 e) coupled together by a plurality ofconnecting pieces (24 a-24 d), and a strip of negative electrode plate(12) formed of a plurality of negative electrode layer faces (23 a-23 f)coupled together by a plurality of connecting pieces (25 a-25 e) at therespective connecting pieces (24 a-24 d, 25 a-25 e) and coiling itaround into an electrode plate group (10) of flat form such that thepositive electrode layer faces (22 a-22 e) and the negative electrodelayer faces (23 a-23 f) are alternately layered upon one another with aseparator (13) interposed therebetween; accommodating the electrodeplate group (10) into a sealing case (5); injecting liquid electrolytethereinto; placing a cap case (4) onto the sealing case (5) via a gasket(6); and crimping the cap case (4) to seal the inside of the sealingcase (5), characterized in that the positive electrode plate (11) andthe negative electrode plate (12) are respectively formed withpositional discrepancy detecting cut-outs (41 a, 41 b, 42, 43, 44, 71 a,71 b, 72, 73, 74) for detecting positional displacement between thepositive electrode layer faces (22 a-22 e) and the negative electrodelayer faces (23 a-23 f) when both electrode plates (11, 12) are coiledaround; after coiling around the positive electrode plate (11) and thenegative electrode plate (12) into the electrode plate group (10),X-rays are irradiated thereto in a direction in which the electrodeplates are layered so as to obtain transmitted X-ray images of theelectrode plate group (10); a positional discrepancy is detected, byprocessing the images, between the positional discrepancy detectingcut-outs (41 a, 41 b, 42, 71 a, 71 b, 72) in the positive electrodelayer faces (22 a, 22 b, 22 e) and the positional discrepancy detectingcut-outs (43, 44, 73, 74) in the negative electrode layer faces (23 a,23 f); and when the detected positional discrepancy is within apredetermined permissible range, the electrode plate group (10) isaccommodated in the sealing case (5).